Radio network controller, mobile station, and mobile communication method

ABSTRACT

A radio network controller comprises a cell selector configured to select a cell to use by a mobile station after data reception, and a mobile station controller configured to control the mobile station to communicate by radio using the cell selected by the cell selector after the data reception.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromprior Japanese Patent Applications No. 2004-233889, filed on Aug. 10,2004, No. 2004-278310, filed on Sep. 24, 2004, and No. 2005-41415, filedon Feb. 17, 2005; the entire contents of which are incorporated hereinby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a radio network controller, a mobilestation, and a mobile communication method.

2. Description of the Related Art

Conventionally, a service (Multimedia Broadcast Multicast Service,hereinafter, referred to as an “MBMS”) has been provided, in whichmultimedia contents are broadcasted or multicasted to plural mobilestations (3GPP TSG-RAN, “TS25.346 V6.1.0 Introduction of Multimediabroadcast multicast service (MBMS) in Radio access network (RAN)”, June,2004). In the MBMS, a frequency at which data is transmitted by the MBMSis notified to the mobile station via a radio access network. Due tothis, it is possible for the mobile station not receiving data currentlythrough the MBMS to receive data through the MBMS by carrying out afrequency handover to the notified frequency.

However, the mobile station that has started to use a specific frequencyat which data is transmitted through the MBMS continues to be present atthe frequency also after data reception through the MBMS unless thecommunication quality at the frequency is deteriorated. Therefore,traffic concentrates on a specific frequency and a deviation in thetraffic occurs among frequencies. Such a problem arises not only in theMBMS, but also, for example, when the mobile station receives data to betransmitted by using a specific frequency such as a case of a high speeddownlink packet access (HSDPA) etc or the like. Concentration of thetraffic on one part of the frequencies as described above brings about awaste in utilizing radio resources.

SUMMARY OF THE INVENTION

An object of the present invention is to prevent traffic fromconcentrating after data reception and to effectively utilize radioresources.

A radio network controller according to an embodiment of the presentinvention includes a cell selector configured to select a cell to use bya mobile station after data reception, and a mobile station controllerconfigured to control the mobile station to communicate by radio usingthe cell selected by the cell selector after the data reception.

The radio network controller can select a cell that the mobile stationuses after data reception and make the mobile station to use theselected cell. Therefore the radio network controller can preventtraffic from concentrating and effectively utilize the radio resourcesby distributing mobile stations to plural cells after data reception.

A mobile station according to an embodiment of the present inventionincludes a radio communication unit configured to communicate by radio,and a communication controller configured to select a cell to use afterdata reception and control the radio communication unit to communicateby radio using a selected cell after the data reception.

The mobile station can select a cell that the mobile station uses afterdata reception and communicate by radio using the selected cell afterdata reception. Therefore, the mobile stations can be distributed toplural cells after data reception. As a result, the mobile station canprevent traffic from concentrating and effectively utilize radioresources.

A mobile communication method according to an embodiment of the presentinvention includes selecting a cell to use by a mobile station afterdata reception, and communicating by radio using a selected cell afterthe data reception by the mobile station.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a mobile communication system according toan embodiment of the present invention.

FIG. 2 is a diagram showing a state before a frequency handoveraccording to an embodiment of the present invention.

FIG. 3 is a diagram showing a state after a frequency handover accordingto an embodiment of the present invention.

FIG. 4 is a block diagram showing a radio network controller accordingto an embodiment of the present invention.

FIG. 5A is a diagram showing an MCCH signal according to an embodimentof the present invention and FIG. 5B is a diagram showing a BCCH signalaccording to an embodiment of the present invention.

FIG. 6 is a block diagram showing a mobile station according to anembodiment of the present invention.

FIG. 7 is a diagram showing a state after data reception according to anembodiment of the present invention.

FIG. 8 is a flow chart showing an operation procedure of the radionetwork controller according to an embodiment of the present invention.

FIG. 9 is a flow chart showing an operation procedure of the mobilestation according to an embodiment of the present invention.

FIG. 10 is a block diagram showing a radio network controller accordingto a modification example of the present invention.

FIG. 11 is a block diagram showing a mobile station according to amodification example of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(Mobile Communication System)

As shown in FIG. 1, a mobile communication system 100 includes mobilestations 10, base stations 20, a radio network controller 30, a corenetwork 40, and a contents server 50.

The contents server 50 provides an MBMS (Multimedia Broadcast MulticastService) that broadcasts or multicasts multimedia contents and the liketo plural mobile stations 10. The contents server 50 broadcasts ormulticasts the multimedia contents and the like to the plural mobilestations 10 via the core network 40, the radio network controller 30,and the base stations 20.

The radio network controller 30 controls radio communication between thebase stations 20 and the mobile stations 10. The base stations 20 andthe mobile stations 10 communicate by radio under control by the radionetwork controller 30. The mobile stations 10 transmit/receive data orcontrol signals to/from the radio network controller 30 and the contentsserver 50 via the base stations 20.

The mobile communication system 100 covers plural areas. Each area isdivided into plural cells by a position and frequency. In the mobilecommunication system 100, one area is divided by plural frequencies andone area has a layered structure based on plural frequencies. Each areadivided by frequencies is further divided by a position and thus pluralcells are formed. As described above, the cell is a communication regiondivided by the frequency and position.

The mobile communication system 100 providing the MBMS performs an FLCprocess (Frequency Layer Convergence process). The FLC process includesnotifying the mobile station 10 of the frequency at which the data ofthe MBMS is transmitted (hereinafter, referred to as a “targetfrequency”) and making the mobile station 10 to receive the data of theMBMS at the target frequency. The radio network controller 30 transmitsa control signal to the mobile station 10 via the base station 20,thereby the FLC process is performed. Specifically, the radio networkcontroller 30 notifies the mobile station 10 of the target frequency bytransmitting a control signal called LCI (Layer Convergence Information)to the mobile station 10. The LCI can include an offset value of thetarget frequency from the frequency, which the mobile station 10currently uses (hereinafter, referred to as an “in-use frequency”), forexample.

The FLC process is explained in detail using FIG. 2 and FIG. 3. FIG. 2and FIG. 3 show cells 101 to 104 divided by four frequencies FA1 to FA4.Although not shown schematically, there exist plural cells of which theposition is different at each of the frequencies FA1 to FA4.

As shown in FIG. 2, before data transmission by the MBMS, the mobilestations 10 are present at the respective cells 101 to 104 of therespective frequencies FA1 to FA4. When the data by the MBMS istransmitted using the frequency FA4, the radio network controller 30notifies the mobile stations 10 of the target frequency FA4 via the basestations 20. The radio network controller 30 notifies the targetfrequency FA4 through an MCCH (MBMS Control CHannel) at each of thefrequencies FA1 to FA4 via the base station 20. The MCCH is a broadcastchannel for transmitting a control signal regarding the MBMS. Forexample, the LCI including the offset value of the target frequency FA4from the in-use frequency FA3 is transmitted to the mobile stations 10being present in the cell 103, and thus the target frequency is notifiedto the mobile stations 10.

The mobile stations 10 that intend to receive the data by the MBMS (themobile stations circled by the dotted line in FIG. 2) receive the LCItransmitted through the MCCH. Then, the mobile stations 10 carry out afrequency handover to the target frequency FA4. In other words, themobile stations 10 connect to the base station 20 that covers the cell104 of the frequency FA4 and start radio communication using thefrequency FA4. As a result of the frequency handover, as shown in FIG.3, the mobile stations 10 that intend to receive the data by the MBMSmove to the cell 104 of the frequency FA4. Then, the mobile stations 10receive the data provided by the MBMS using the frequency FA4.

Next, the radio network controller 30 and the mobile station 10 areexplained in detail. As shown in FIG. 4, the radio network controller 30includes a cell selector 31, a mobile station controller 32, and atransmitter/receiver 33. The transmitter/receiver 33 transmits/receivescontrol signals and data to/from the mobile stations 10 via the basestations 20.

The cell selector 31 selects a cell to use by the mobile station 10after data reception. The cell selector 31 preferably selects a cell touse by the mobile station 10 after at least one of reception of data bybroadcast, reception of data by multicast, and reception of datatransmitted by a high speed downlink packet access (HSDPA). According tothis, the radio network controller 30 can distribute mobile stations,which receive data transmitted using a specific frequency or datatransmitted to the mobile station located at a specific position, suchas broadcast, multicast, or data transmission by the HSDPA, andconcentrate on a specific frequency or position, i.e., a specific cell,to cells having different frequencies and positions.

The cell selector 31 can select a cell to use after data reception basedon, for example, at least one of a use history of the cell by the mobilestation 10, a use status of radio resources in the cell, the number ofmobile stations being present in the cell, a propagation path state inthe cell, neighboring cell information about the cell neighboring thecell the mobile station 10 uses at the data reception, and communicationquality in the cell. According to this, the radio network controller 30can more appropriately distribute the mobile stations 10 inconsideration of these kinds of information and more effectively utilizeradio resources. The cell selector 31 can also select a cell randomly.According to this, a control load of the radio network controller 30 canbe reduced.

The use history of the cell includes, for example, the cell in which themobile station 10 has transmitted/received data thus far, the cell inwhich the mobile station 10 currently transmits/receives data, the cellin which the mobile station 10 has been standby thus far, the cell inwhich the mobile station 10 is currently standby, a presence period inthe cell, a presence frequency in the cell, an order of using the cell,time of data transmission/reception, time of presence in the cell andthe like.

The cell selector 31, when selecting a cell based on the use history ofthe cell, preferably selects a cell, of which the frequency is the sameas that of the cell, in which the mobile station 10 was present justbefore data reception, and which the mobile station 10 used just beforedata reception, as a cell to use after data reception. According tothis, the radio network controller 30 can return the mobile station 10to the frequency that the mobile station 10 used just before the datareception. For example, the cell selection section 31 can select a cell,of which the frequency is the same as that of the cell the mobilestation 10 used just before data reception, and which is usable at thecurrent position of the mobile station 10, as a cell to use after datareception. Further, the cell selector 31 can also select a cell of whichthe presence period or the presence frequency is high.

The cell selector 31 can request the base station 20 via thetransmitter/receiver 33 to notify the use history of the cell by themobile station 10, the use status of radio resources in the cell, thenumber of mobile stations being present in the cell, the propagationpath state in the cell, the communication quality in the cell and thelike. Further, the cell selector 31 also can obtain neighboring cellinformation by determining a cell that the mobile station 10 uses atdata reception based on the use history of the cell by the mobilestation 10.

The cell selector 31 can select a cell to use by the mobile station 10after data reception from among the plural cells. For example, the cellselector 31 can select a cell from the cells, of which the frequency isthe same as that of the cell the mobile station 10 uses currently, andwhich neighbor the cell the mobile station 10 uses currently, the cells,which neighbor the cell the mobile station 10 uses currently, and ofwhich the frequency is different from that of the cell the mobilestation 10 uses currently, and the cells, of which the frequency isdifferent from that of the cell the mobile station 10 uses currently,and which neighbor the cell the mobile station 10 uses currently.

In this manner, the cell selector 31 can select a frequency(hereinafter, referred to as a “preferred frequency”) of the cell to useby the mobile station 10 after data reception.

The cell selector 31 may select one cell or plural cells as candidates.The cell selector 31 may set priorities of use when selecting pluralcells. For example, the cell selector 31 can set the priorities based onat least one of the use history of the cell by the mobile station 10,the use status of radio resources in the cell, the number of mobilestations being present in the cell, the propagation path state in thecell, the neighboring cell information, and the communication quality inthe cell.

Further, the cell selector 31 may set the priorities randomly. Forexample, the cell selector 31 can randomly determine a first selectioncandidate from among the cells of which the frequency is usable by themobile station 10, and set the highest priority to the first selectioncandidate. The cell selector 31 can randomly determine a secondselection candidate and subsequent candidates, and set the priorities tothe candidates sequentially.

Further, the cell selector 31 may set the priorities by the valuecalculated from the following Expression (1) using an identifierinherent to the mobile station 10.

Identifier of the mobile station modN Expression (1)

(Where N=the number of cells the mobile station can use)

As an identifier inherent to the mobile station 10, for example, an IMSI(International Mobile Subscriber Identity) and the like can be used. Thecell selector 31 stores a table of correspondence between the calculatedvalues of Expression (1) and the identifiers (cell IDs) for identifyinga cell in advance. Then, the cell selector 31 calculates Expression (1),refers to the table of correspondence based on the calculated value, andselects a cell having a cell ID corresponding to the calculated value.

Further, the cell selector 31 can select cells to use by plural mobilestations 10 after data reception and set ratios (hereinafter, referredto as a “mobile station ratio”) of the mobile stations that should userespective cells to the selected cell. For example, the cell selector 31can set the mobile station ratio of the cell 101 to 40%, that of thecell 102 to 20%, that of the cell 103 to 30%, and that of the cell 104to 10%, respectively. The cell selector 31 can set a high mobile stationratio to a cell, which the cell selector 31 intends to make many mobilestations to use, for example, such as a cell where available radioresources are rich, the number of mobile stations being present thereatis small, the propagation path state is good, the communication qualityis good and the like. On the other hand, the cell selector 31 can set alow mobile station ratio to a cell, in which a few mobile stations canuse, for example, such as a cell where available radio resources arepoor, the number of mobile stations being present thereat is large, thepropagation path state is not good, the communication quality is notgood and the like.

According to this, the radio network controller 30 can make many mobilestations to use the cell that the radio network controller 30 intends tomake many mobile stations to use, and suppress the number of mobilestations that use the cell in which only a few mobile stations can use.Therefore, the radio network controller 30 can distribute the mobilestations 10 appropriately.

The cell selector 31 may select a cell for each mobile station 10, acell for a group of specific mobile stations in common, or a cell forall mobile stations that have received the data transmitted by the MBMSor HSDPA in common.

The cell selector 31 inputs information (hereinafter, referred to as“selected cell information”) about the selected cell into the mobilestation controller 32. As selected cell information, for example, anidentifier for identifying a cell (cell ID), an identifier of a basestation that covers the cell (base station ID), control information forreceiving signals in the cell, the frequency (preferred frequency) ofthe cell, the positional information of the cell and the like can beused. These kinds of information may be used alone or in combination. Asa frequency (preferred frequency) of the cell, for example, an absolutevalue of the frequency of the selected cell (2.0 GHz etc.), or arelative value of the frequency of the selected cell (the offset valueof the frequency of the selected cell from the in-use frequency etc.)can be used. Further, the selected cell information can include thepriorities, the mobile station ratio and the like. The cell selector 31inputs the neighboring cell information as well into the mobile stationcontroller 32. The preferred frequency specified for the mobile station10 is particularly referred to as “preferred frequency information” inthe selected cell information.

The mobile station controller 32 controls the mobile station 10 tocommunicate by radio using the cell selected by the cell selector 31after the data reception. The mobile station controller 32 generates acontrol signal for notifying the mobile station 10 of the selected celland transmits the control signal to the mobile station 10 via thetransmitter/receiver 33. In this manner, the mobile station controller32 notifies the mobile station 10 of the selected cell and controls themobile station 10.

The mobile station controller 32 generates a control signal by using theselected cell information obtained from the cell selector 31. The mobilestation controller 32 generates, for example, a control signal includingthe selected cell information, which is transmitted through radiochannels such as a dedicated channel that is individual for each mobilestation 10, a common channel for the plural mobile stations 10 incommon, and a broadcast channel.

The mobile station controller 32 can, for example, generate an MCCHsignal 1 including the selected cell information 1 a as shown in FIG.5A. The MCCH signal 1 is a control signal regarding the MBMS transmittedthrough the MCCH. The mobile station controller 32 may generate a BCCHsignal 2 including the selected cell information 1 a as shown in FIG.5B. The BCCH signal 2 is a control signal transmitted through a controlchannel called a BCCH (Broadcast Control CHannel). Alternatively, themobile station controller 32 may generate a control signal including theselected cell information transmitted through the control channel of theHSDPA. The mobile station controller 32 may generate the control signalincluding the neighboring cell information.

In addition, when the cell selector 31 selects s a frequency of the cellto use by the mobile station 10 after the data reception, the mobilestation controller 32 can control the mobile station 10 to communicateby radio using the cell of the selected frequency after data receptionby notifying the mobile station of the preferred frequency informationincluding the specified preferred frequency as the selected cellinformation. In this case, the mobile station controller 32 may generatea control signal including the preferred frequency information as theselected cell information.

The mobile station controller 32 carries out a mapping of the generatedcontrol signal onto the corresponding radio channel. The mobile stationcontroller 32 inputs the generated control signal into thetransmitter/receiver 33 and causes the transmitter/receiver 33 totransmit it to the mobile station 10. The transmitter/receiver 33transmits the control signal obtained from the mobile station controller32 to the mobile station 10 in accordance with an instruction by themobile station controller 32. The mobile station controller 32 notifiesthe mobile station 10 of the selected cell information by making thetransmitter/receiver 33 to transmit the control signal including theselected cell information to the mobile station 10 at either timing,that is, in a standby state before data reception, during datareception, or after data reception. In this manner, the mobile stationcontroller 32 can easily control the mobile station 10 to use theselected cell after data reception by transmitting the control signalincluding the selected cell information about the cell, which should beused after data reception, to the mobile station 10.

As shown in FIG. 6, the mobile station 10 includes a communicationcontroller 11 and a radio communication unit 12. The radio communicationunit 12 communicates by radio with the base station 20. The radiocommunication unit 12 receives a control signal including the selectedcell information transmitted from the radio network controller 30 viathe base station 20. The radio communication unit 12 inputs the receivedcontrol signal into the communication controller 11. The radiocommunication unit 12 communicates by radio under the control by thecommunication controller 11.

The communication controller 11 selects a cell to use after datareception, and controls the radio communication unit 12 to communicateby radio using the selected cell after data reception. The communicationcontroller 11 can select a cell to use based on the selection result ofthe cell to use after data reception by the radio network controller 30.In this case, the communication controller 11 controls the radiocommunication unit 12 based on the control signal notifying the selectedcell from the radio network controller 30. Due to this, the mobilestation 10 can easily control by using the selection result from theradio network controller 30.

The communication controller 11 obtains the control signal from theradio communication unit 12. The communication controller 11 obtains theselected cell information from the control signal as the selectionresult. When the number of the cell specified by the selected cellinformation is one, the communication controller 11 determines that theabove cell is a cell to use after data reception. When the number of thecell specified by the selected cell information is plural, thecommunication controller 11 can select a cell to use after datareception from among the plural cells selected by the radio networkcontroller 30 based on at least one of the use history of the cell, theuse status of radio resources in the cell, the number of mobile stationsbeing present in the cell, the propagation path state in the cell, theneighboring cell information about the cell neighboring the cell to useat data reception, and the communication quality in the cell. Due tothis, the mobile stations 10 can be more appropriately distributed inconsideration of these kinds of the information and more effectivelyutilize the radio resources. The communication controller 11 also canrandomly select a cell to use from among the notified cell candidates.This enables the control load of the mobile station 10 to be reduced.

The communication controller 11 can request the base station 20 via theradio communication unit 12 to notify the use history of the cell, theuse status of radio resources in the cell, the number of mobile stationsbeing present in the cell, the propagation path state in the cell, thecommunication quality in the cell and the like. The communicationcontroller 11 can obtain the neighboring cell information from thecontrol signal from the radio network controller 30.

When the priorities of the cell are included in the selected cellinformation, the communication controller 11 can select a cell to use inaccordance with the priorities. For example, the communicationcontroller 11 determines required values for the use status of radioresources in the cell, the number of mobile stations being present inthe cell, the propagation path state in the cell, the communicationquality in the cell, etc in advance. Then the communication controller11 confirms whether or not the use status of the radio resources in thecell, the number of mobile stations being present in the cell, thepropagation path state in the cell, the communication quality in thecell, etc., satisfy the required values, in order of the priorities. Atthe point that a cell satisfying the required values has been detected,the communication controller 11 selects the above cell as a cell to use.

For example, when the cell using the frequency FA1 and the cell usingthe frequency FA2 are notified as candidates for a cell to use afterdata reception and the cell using the frequency FA1 having a higherpriority than the cell using the frequency FA2, the communicationcontroller 11 first checks the communication quality etc. in the cell ofthe frequency FA1. If the cell of the frequency FA1 satisfies therequired value, the communication controller 11 selects the cell of thefrequency FA1. On the other hand, if the cell of the frequency FA1 doesnot satisfy the required value, the communication controller 11 checksthe cell of the frequency FA2.

When the mobile station ratios are included in the selected cellinformation, i.e., the selection result by the radio network controller30 includes cells to use by the mobile stations 10 after data receptionand ratios (mobile station ratios) of the mobile stations 10 usingrespective cells, the communication controller 11 can select a cell touse after data reception based on the mobile station ratios. Thecommunication controller 11 can preferentially select a cell having ahigher mobile station ratio. As a result, the mobile station 10 can usethe cell having a high mobile station ratio as frequently as possible,which the radio network controller 30 intends to cause many mobilestations to use, and does not use the cell having a low mobile stationratio if possible, which is usable by only a few mobile stations.Therefore, the mobile stations 10 can be distributed properly.

In addition, when the selected cell information is preferred frequencyinformation, i.e., the selection result by the radio network controller30 includes a frequency of the cell to use by the mobile station 10after data reception, the communication controller 11 can select thecell of the preferred frequency specified by the preferred frequencyinformation as the cell to use after data reception. When the preferredfrequency is not specified, the communication controller 11 may selectthe cell to use from all frequencies.

The communication controller 11 may select a cell without using theselection result by the radio network controller 30. For example, thecommunication controller 11 can determine a cell to use after datareception based on at least one of the use history of the cell, the usestatus of radio resources in the cell, the number of mobile stationsbeing present in the cell, the propagation path state in the cell, theneighboring cell information, and the communication quality in the cell.For example, the communication controller 11 can select a cell of whichthe frequency is the same as that of the cell used just before the datareception as a cell to use after data reception. Due to this, the mobilestation 10 can return the frequency, which the mobile station 10 usedjust before the data reception. For example, the communicationcontroller 11 can select a cell, which has the same frequency as that ofthe cell used just before data reception and is usable at the currentposition of the mobile station 10, as a cell to use after datareception. The communication controller 11 also can randomly select acell. This enables the control load of the mobile station 10 to bereduced.

When the number of the cells specified by the selected cell informationis plural, or the cell is selected without using the selection result bythe radio network controller 30, the communication controller 11 may setthe priority of the cell by itself. The communication controller 11 canset the priority based on at least one of the use history of the cell,the use status of radio resources in the cell, the number of mobilestations being present in the cell, the propagation path state in thecell, the neighboring cell information, and the communication quality inthe cell.

Alternatively, the communication controller 11 may set the priorityrandomly. For example, the communication controller 11 can randomlydetermine a first selection candidate from among the cells of thefrequency that the mobile station 10 can use and to give the highestpriority to the first selection candidate. The communication controller11 can randomly determine a second selection candidate and subsequentcandidates, and set the priorities to the candidates sequentially.Further, the cell communication controller 11 may set the priorities bythe value calculated from the above-mentioned Expression (1) using theidentifier inherent to the mobile station 10. In this case, thecommunication controller 11 stores a table of correspondence between thevalues calculated by Expression (1) and the cell IDs in advance.

The case where the communication controller 11 sets the priorities tothe cells in the order of the cell of the frequency FA3, the cell of thefrequency FA2, the cell of the frequency FA4, and the cell of thefrequency FA1 by using any one of the methods described above, that is,the case where the highest priority is set to the cell of the frequencyFA3 and the lowest priority is set to the cell of the frequency FA1, isexplained.

First, the communication controller 11 checks the communication quality,the propagation path state, etc., of the cell of the frequency FA3having the highest priority and determines whether or not the cell ofthe frequency FA3 satisfies the required value. When the required valueis satisfied, the communication controller 11 selects the cell of thefrequency FA3. On the other hand, if the required value is notsatisfied, the communication controller 11 determines whether or not thecell of the frequency FA2 having the second highest priority satisfiesthe required value similarly. In this manner, the communicationcontroller 11 continues to check the state of the cells in the setpriority order until the cell of the frequency that satisfies therequired value is found.

The communication controller 11 controls the radio communication unit 12to start a standby or start transmission and reception of new data afterdata reception by using the selected cell. The communication controller11 preferably selects a cell to use after at least one of the receptionof the data by the broadcast, the reception of the data by themulticast, and the reception of the data transmitted by the high speeddownlink packet access.

For example, as shown in FIG. 3, the mobile station 10 receives the dataprovided by the MBMS in the cell 104 by using the frequency FA4. Whenhaving selected, for example, the cell 103 as a cell to use after datareception by the MBMS, the communication controller 11 instructs theradio communication unit 12 to carry out a frequency handover to thefrequency FA3. The radio communication unit 12 connects to the basestation 20 that covers the cell 103 of the frequency FA3 and startsradio communication using the frequency FA3.

Due to this, as shown in FIG. 7, for example, after the data receptionby the MBMS, the several mobile stations 10 (mobile stations circled bythe dotted line in FIG. 7) switch their cells from the cell 104 to thecell 103 or the cell 101 for use, thus making the distribution possible.The cell selector 31 of the radio network controller 30 or thecommunication controller 11 of the mobile station 10 selects a cell thatthe mobile station 10 uses after data reception so that traffic does notconcentrate on one cell but the mobile stations 10 are distributed toeach cell as shown in FIG. 7.

(Mobile Communication Method)

Next, the mobile communication method in the mobile communication system100 is explained. FIG. 8 shows the operation procedure of the radionetwork controller 30. The radio network controller 30 selects a cell touse by the mobile station 10 after data reception (S101). The radionetwork controller 30 generates a control signal including the selectedcell information (S102). The radio network controller 30 transmits thegenerated control signal to the mobile station 10 via the base station20 (S103).

FIG. 9 shows the operation procedure of the mobile station 10. Themobile station 10 receives the control signal from the radio networkcontroller 30 via the base station 20 (S201). The mobile station 10selects a cell to use after data reception by using the cell selectioninformation included in the received control signal (S202). After thedata reception, the mobile station 10 starts a standby or startstransmission and reception of new data using the selected cell (S203).The mobile station 10 may omit the step (S201) and select a cell in itsown way.

According to the mobile communication system 100, the radio networkcontroller 30, the mobile station 10, and the mobile communicationmethod described above, the radio network controller 30 can select acell that the mobile station 10 is made to use after data reception andto cause the mobile station to use the selected cell after datareception. Further, the mobile station 10 can select a cell to use afterdata reception, and communicate by radio using the selected cell afterdata reception. Therefore, it is possible to distribute the mobilestations 10 to plural cells after data reception, to prevent the trafficfrom concentrating, and to utilize the radio resources effectively. Forexample, when the mobile station 10 receives data transmitted using aspecific frequency or data transmitted to a mobile station located in aspecific position like a case of receiving data by the MBMS or ofreceiving data by the HSDPA, the mobile stations 10 concentrating on aspecific frequency or position can be distributed as evenly as possibleto the cells of different frequencies or positions after data reception.Therefore, the traffic can be prevented from slanting to a specificfrequency or position and an effective use of the radio resources can beexpected.

MODIFICATION EXAMPLE

Although the inventions have been described above by reference tocertain embodiments of the inventions, the inventions are not limited tothe embodiments described above. Modifications and variations of theembodiments described above will occur to those skilled in the art, inlight of the above teachings. For example, a radio network controller230 shown in FIG. 10 may be used. The radio network controller 230includes a cell information storage unit 34, a cell selector 231, themobile station controller 32, and the transmitter/receiver 33. The cellinformation storage unit 34 stores the use history of the cell relatingto each mobile station 10. In this case, the cell selector 231 refers tothe cell information storage unit 34 and selects the cell to use afterdata reception using the use history of the cell stored in the ellinformation storage unit 34. Due to this, the radio network controller30 can easily select the cell using the use history. The cell selector231 stores the use history obtained from the base station 20 in the cellinformation storage unit 34.

Alternatively, a mobile station 210 shown in FIG. 11 may be used. Themobile station 210 includes a cell information storage unit 13, acommunication controller 211, and the radio communication unit 12. Thecell information storage unit 13 stores the use history of the cell ofthe mobile station 210 itself. In this case, the communicationcontroller 211 can refer to the cell information storage unit 13 andselect a cell to use after data reception. The communication controller211 stores the use history of the mobile station 210 itself in the cellinformation storage unit 13. Due to this, the mobile station 210 canrefer to the cell information storage unit 13 and select a cell in itsown way. The cell information storage units 34 and 13 may storeinformation other than the use history obtained from the base station20.

Further, the cell selector 31 may select a cell of the frequency otherthan the banned frequency as a cell to use after data reception, bydetermining the banned frequency. The banned frequency is a frequency,which the mobile station is banned from using after data reception. Inthis case, the mobile station controller 32 can control the mobilestation 10 to communicate by radio using the cell of the frequency otherthan the banned frequency after data reception by notifying the mobilestation 10 of the banned frequency.

Due to this, the radio network controller 30 can determine the bannedfrequency that the mobile station 10 is banned from using after datareception, and to cause the mobile station 10 to use the cell of thefrequency other than the banned frequency. Therefore, the radio networkcontroller 30 can distribute the mobile stations 10 to the cell of thefrequency other than the frequency, which the radio network controller30 intends to cause the mobile stations 10 not to use after datareception, prevent the traffic from concentrating, and effectivelyutilize the radio resources. The cell selector 31 can, for example,determine the banned frequency based on the use status of thefrequencies. For example, the mobile station control section 32 cangenerate the control signals such as the MCCH signal and the BCCH signalincluding the banned frequency and notify the mobile station 10 of thebanned frequency in the same manner as the case of notifying the cellselection information.

In this case, the communication controller 11 of the mobile station 10can select a cell of the frequency other than the banned frequencydetermined by the radio network controller 30 as a cell to use afterdata reception. Due to this, the mobile stations 10 can be distributedto the cell of the frequency other than frequencies that the radionetwork controller 30 intends to cause the mobile stations 10 not touse. The communication controller 11 obtains the control signalincluding the banned frequency in the same manner as the case of thecell selection information. Then, the communication controller 11 canselect a cell of the frequency other than the banned frequency includedin the control signal as a cell to use.

1. A radio network controller comprising: a cell selector configured toselect a cell to use by a mobile station after data reception; and amobile station controller configured to control the mobile station tocommunicate by radio using the cell selected by the cell selector afterthe data reception.
 2. The radio network controller according to claim1, wherein the cell selector selects a frequency of the cell to useafter the data reception, and the mobile station controller controls themobile station to communicate by radio using the cell of the frequencyafter the data reception
 3. The radio network controller according toclaim 1, wherein the mobile station controller generates a controlsignal for notifying the mobile station of a selected cell.
 4. The radionetwork controller according to claim 1, wherein the cell selectorselects cells to use by mobile stations after the data reception, andsets ratios of the mobile stations using respective cells to selectedcells.
 5. The radio network controller according to claim 1, wherein thecell selector selects the cell to use after the data reception based onat least one of a use history of the cell by the mobile station, a usestatus of radio resources in the cell, the number of mobile stationsbeing present in the cell, a propagation path state in the cell,neighboring cell information about the cell neighboring the cell themobile station uses at the data reception, and communication quality inthe cell.
 6. The radio network controller according to claim 5, whereinthe cell selector selects a cell of a frequency, which the mobilestation used just before the data reception as the cell to use after thedata reception.
 7. The radio network controller according to claim 5,further comprising: a cell information storage unit configured to storethe use history of the cell, wherein the cell selector selects the cellto use after the data reception by referring to the cell informationstorage unit.
 8. The radio network controller according to claim 1,wherein the cell selector selects the cell to use after the datareception randomly.
 9. The radio network controller according to claim1, wherein the cell selector selects a cell of a frequency other than abanned frequency, which the mobile station is banned from using, as thecell to use after the data reception by determining the bannedfrequency, and the mobile station controller controls the mobile stationto communicate by radio using the cell of the frequency other than thebanned frequency after the data reception, by notifying the mobilestation of the banned frequency.
 10. The radio network controlleraccording to claim 1, wherein the cell selector selects the cell to useafter at least one of reception of data by broadcast, reception of databy multicast, and reception of data transmitted by a high speed downlinkpacket access.
 11. A mobile station comprising: a radio communicationunit configured to communicate by radio; and a communication controllerconfigured to select a cell to use after data reception and control theradio communication unit to communicate by radio using a selected cellafter the data reception.
 12. The mobile station according to claim 11,wherein the communication controller selects the cell to use after thedata reception based on a selection result of the cell to use after thedata reception by a radio network controller.
 13. The mobile stationaccording to claim 12, wherein the selection result includes a frequencyof the cell to use after the data reception, and the communicationcontroller selects the cell of the frequency as the cell to use afterthe data reception.
 14. The mobile station according to claim 12,wherein, the selection result includes cells to use by mobile stationsafter the data reception and ratios of the mobile stations usingrespective cells, and the communication controller selects the cell touse after the data reception based on the ratios of the mobile stations.15. The mobile station according to claim 11, wherein the communicationcontroller selects the cell to use after the data reception based on atleast one of a use history of the cell, a use status of radio resourcesin the cell, the number of mobile stations being present in the cell, apropagation path state in the cell, neighboring cell information aboutthe cell neighboring the cell to use at the data reception, andcommunication quality in the cell.
 16. The mobile station according toclaim 15, wherein the communication controller selects a cell of afrequency used just before the data reception as the cell to use afterthe data reception.
 17. The mobile station according to claim 15,further comprising: a cell information storage unit configured to storethe use history of the cell, wherein the communication controllerselects the cell to use after the data reception by referring to thecell information storage unit.
 18. The mobile station according to claim11, wherein the communication controller selects the cell to use afterthe data reception randomly.
 19. The mobile station according to claim11, wherein the communication controller selects a cell of a frequencyother than a banned frequency, which the mobile station is banned fromusing and is determined by the radio network controller, as the cell touse after the data reception
 20. The mobile station according to claim11, wherein the communication controller selects the cell to use afterat least one of reception of data by broadcast, reception of data bymulticast, and reception of data transmitted by a high speed downlinkpacket access.
 21. A mobile communication method comprising: selecting acell to use by a mobile station after data reception; and communicatingby radio using a selected cell after the data reception by the mobilestation.